Script engine support for Balance #983

[AwooOOoo]

Added balance support into the script engine (#983). It is set up similar to setTick in that it takes a callback and the trading pair to return the balance on.

Fields Available
The balance exposes the following fields;
[currency=ETH, total=1000, available=1000, frozen=0, borrowed=0, loaned=0, withdrawing=0, depositing=0]

Note that the response is called twice, once for the base and once for the quote. Assuming you had ETH/EUR selected, in the example below, it would call the function once for ETH and once for EUR.

Example Usage:

function start() {
  var subscription = balance.get(
    function(event) {
      var b = event.balance();  
      notifications.info("Balance: " + b.currency + " - " + b.available);
    },
    parameters.selectedCoin
  );
  
  return RUNNING
}

function stop() {
  events.clear(subscription);  // Stop the subscription
}

Output from Example:

Possible Improvements:

1. Since it is already a balance.get() call, perhaps don't have the .balance() on the return
2. Combine returns so you can access .base() & .count() at the same time to ensure they are not out of sync
3. Make it a single call and not a subscription

Thoughts?

[AwooOOoo]

@badgerwithagun - I've made some mark down updates on some of the wikis, but don't have permission to push changes and can't fork to do a PR. Whats the best way to submit them?

[badgerwithagun]

This looks great. Could we move the new method toEvents, though, and use the same call pattern as for tickets, e.g. setBalance, with the assumption that it will be called again on shutdown to release the subscription?

[badgerwithagun]

One other thought, probably not one to solve here, is that the ticker and balance event objects are not version controlled DTOs, and we should probably create some for this. If those objects change, we can't have that propagating to the script API without careful consideration.

[AwooOOoo]

@badgerwithagun ,
No worries, I'll move it to Events. Assign the issue to me also. Good point on the versioning, I'll have a think about it.

[badgerwithagun]

Looking good! Just one small cleanup then I think we're good to go.

[badgerwithagun]

One more thing: could you extend the testing in TestScriptJobProcessor to cover these use cases?

[AwooOOoo]

Code Cleanup submitted. Its going to take me a little bit to wrap my head around how to write those test cases well.

[AwooOOoo]

Is there a shortcut to just running the TestScriptJobProcessor tests? I'm still getting familiar with the environment.

[badgerwithagun]

Do you use a Java IDE, @AwooOOoo ?

This is easy in IntelliJ, just right-click and run.

[AwooOOoo]

@badgerwithagun Currently using Visual Studio Code. I installed eclipse, but haven't gotten into it yet and it seems to have a steep learning curve. Sorry if the PR's aren't efficient. I haven't programmed Java in many years and so am pretty damn rusty. I appreciate the hints, its a lot to take in trying to remember the language and take in the code base.

[badgerwithagun]

@badgerwithagun Currently using Visual Studio Code. I installed eclipse, but haven't gotten into it yet and it seems to have a steep learning curve. Sorry if the PR's aren't efficient. I haven't programmed Java in many years and so am pretty damn rusty. I appreciate the hints, its a lot to take in trying to remember the language and take in the code base.

Got it. FWIW, IntelliJ is by far the easiest to use with this codebase. If you load it as a Maven project it will work out of the box with no further configuration.

[AwooOOoo]

This is easy in IntelliJ, just right-click and run.

It is easy with IntelliJ, thanks =)

[badgerwithagun]

Merged. Thanks @AwooOOoo :)

[AwooOOoo]

@badgerwithagun There is a PR in the wiki, that covers the changes. I'll add the unit tests when I get some time.